I know there could be a lot of things that can cause P0300 errors so hoping someone might be able to help narrow it down. A couple of months ago it started running really rough after the car was running for a few minutes. Took it to the dealer and they were seeing P0300 errors. Initially they told me they couldn't diagnose it and wanted to replace all coils but after I told them to try harder they eventually replaced 1 coil pack and it's been running fine since. The other day it started again but now it doesn't start until about 30 mins of driving. Check Engine light blinks on and off and sometimes comes on solid. It's happening while driving highway conditions and it's intermittent, meaning once it starts missing, it comes and goes. I can feel it kick in and out randomly while driving. It's an 04 Roadster with 77K miles but the motor was replaced at 62K by Nissan so it's low miles. I don't know what parts they swapped from the old to the new one so don't know if the coils are 8 yrs old with 77K on them or relatively new. I've read other posts about possible vacuum leaks, bad coils, throttle body etc, but the intermittent nature of it make me think electronics. Any thoughts on how to better isolate the cause?

 

No one has any ideas? I'd really appreciate any help or words of wisdom.

 

What is done to the motor?

 

I beleive p0300 is random misfires. Have you checked the spark plugs? Replaced it.

Do you use premium fuel? If not, switch to premium.

 

I had the same code. For me, it was a leaky injector. Pull all the spark plugs out one by one and look for the black one. Change the corresponding injector. Total cost was around $200, but I had bought all new seals for the injectors on the rail I pulled off, new gaskets for the intake plenum, and finally the cost of the injector itself.

Good luck!

 

im yet another victime of the MISFIRE problem.

i am going to try this and see if it helps me!! if not then on to the next suggestion.

 

i took out all 6 injectors in search of the "black" one which would indicate a faulty leaky injector.. they all look very similar to me.. and the tips all look white. can anyone confirm this? or is anyone able to see the faulty one?

 

I had fuel coming out my tailpipes. The stuck injector was spraying even when the intake valve was closed, so fuel was bouncing up into the plenum and being sucked in by all cylinders. As far as I can tell, of your plugs look decent. It was obvious for me. Not sure where to guide you from here.